The present invention relates generally to the fields of gene expression, particularly tissue specific expression, and more particularly smooth muscle cell specific expression. The invention also relates to cell proliferation diseases such as atherosclerosis, restenosis following balloon angioplasty and airway blockage in asthma.
The phenotypic plasticity of smooth muscle cells (SMCs) permits this muscle cell lineage to subserve diverse functions in multiple tissues including the arterial wall, uterus, respiratory, urinary and digestive tracts. In contrast to fast and slow skeletal muscle cells which fuse and terminally differentiate before expressing contractile protein isoforms, SMCs are capable of simultaneously proliferating and expressing a set of lineage-restricted proteins including myofibrillar isoforms, cell surface receptors and SMC-restricted enzymes. Moreover, in response to specific physiological and pathophysiological stimuli, SMCs can modulate their phenotype by down-regulating a set of contractile protein genes, and in so doing, convert from the so called “contractile phenotype” to a de-differentiated “secretory phenotype” (Mosse et al., Lab Invest., 53:556–562, 1985; Owens et al., J. Cell Biol., 102:343–352, 1986; Rovner et al., J. Biol. Chem., 261:14740–14745, 1986; Taubman et al., J. Cell Biol., 104:1505–1513, 1987; Ueki et al., Proc. Natl. Acad. Sci. USA, 84:9049–9053, 1987; Belkin et al., J. Biol. Chem., 263:6631–6635, 1988; Glukhova et al., Proc. Natl. Acad. Sci. USA., 85:9542–9546, 1988; Chaponnier et al., Eur. J. Biochem., 190:559–565, 1990; Gimona et al., FEBS Letters, 274: 159–162, 1990; Shanahan et al., Circ. Res., 73:193–204, 1993).
This phenotypic modulation has been implicated in the pathogenesis of a number of disease states including atherosclerosis and restenosis following coronary balloon angioplasty (Ross, N. Engl. J. Med. 314:488–500, 1986; Schwartz et al., Circ. Res., 58:427–440, 1986; Zanellato et al., Arteriosclerosis, 10:996–1009, 1990; Ross, Am. J. Pathol., 43:987–1002, 1993; Olson and Klein, Genes Dev., 8:1–8, 1994) and may also contribute to the airway remodeling seen in asthma (James et al., Am. Rev. Respir. Dis., 139:242–246, 1989). Restenosis following coronary balloon angioplasty is a major problem, and contributes to the 40% failure rate of this procedure (Schwartz et al., 1992; Liu et al., Circ. 79:1374–1387, 1989). Restenosis occurs because the smooth muscle cells are stimulated to proliferate after angioplasty and thus block the arterial wall. Because of restenosis, balloon angioplasty is used mainly for palliation in patients who are not acceptable candidates for open heart surgery (Scientific American Medicine, Rubenstein and Federman, Eds., March 1993, Section 1, XII, page 11). A method is needed, therefore, to control or inhibit the proliferation of smooth muscle cells after angioplasty.
Although RDAd efficiently transduce both resting and proliferating SMCs in vivo, a potential limitation of their use in the clinical setting is their capacity to infect and program transgene expression in many different cell lineages and tissues (Ohno et al., Science, 265 (5173):781–784, 1994; Haddada et al., Current Topics in Microbiology & Immunolog,. 199 (Pt 3):297–306, 1995). For example, localized arterial administration of RDAd results in efficient infection of endothelial cells, vascular SMCs and adventitial cells (French et al., Circulation, 90 (5):2402–2413, 1994; Simari et al., J. Clin. Invest., 98 (1):225–235, 1996). Moreover, intravenous administration of these vectors results in high-level gene transfer to the liver and lung (Kashyap et al., J. Clin. Invest. 96 (3):1612–1620, 1995; Johns et al., J. Clin. Invest. 96 (2):1152–1158, 1995; Miller and Vile, FASEB Journal, 9 (2):190–199, 1995). Several approaches have been used in an attempt to circumvent this problem. First, it has been possible to restrict the expression of a viral transgene to a specific cell or tissue by administering the virus ex vivo. However, this approach is laborious and is not practical for the treatment of most vascular proliferative disorders. A second approach has involved delivery of adenoviral particles locally within the vasculature (to the site of vessel wall injury) or within a tissue (Ohno et al., 1994; Chang et al., Science, 267:518–522, 1995a; Guzman et al., 1994; Chang et al., Mol. Medicine, 1:172–181, 1995b). Specially-modified catheter delivery systems including coated-balloons and intravascular stents have been designed in order to achieve high local concentrations of adenovirus within the vasculature (March et al., Human Gene Therapy, 6 (1):41–53, 1995; Rajasubramanian et al., ASAIO Journal, 40 (3):M584–M589, 1994; Kito et al., ASAIO Journal, 40 (3):M260–M266, 1994). However, the usefulness of these approaches may be limited within the human coronary circulation due to the high frequency of side branches. Moreover, such catheter delivery systems do not restrict transgene expression to specific cell types in the vessel wall. Finally, several groups have reported that the tissue-tropism of RDAd can be modified by electrostatically conjugating adenoviral proteins to ligands that can bind specifically to tissue-specific cell-surface receptors (Krasnykh et al., Journal of Virology, 70 (10):6839–6846, 1996). This approach has been used to successfully target RDAd to hepatocytes and hematopoietic progenitor cell lines (Schwarzenberger et al., Blood, 87 (2):472–478, 1996).
The use of tissue-specific transcriptional regulatory elements represents an alternative strategy to restrict adenoviral transgene expression to specific cell lineages or tissues in vivo (Miller and Vile, 1995). While theoretically appealing, this strategy is potentially limited because the adenovirus genome contains multiple highly active transcriptional enhancers that are capable of transactivating a variety of different promoters in multiple cell lineages (Haddada et al., 1995). Such a targeting strategy is particularly problematic in smooth muscle cells because of the lack of smooth muscle cell-specific transcriptional regulatory elements that function in vivo. Thus, there is still a need for discovery of a smooth muscle cell specific promoter that is not expressed in other types of cells and is constitutively expressed in both quiescent and proliferating cells and that maintains its tissue specificity when administered to an animal.